This research examines how young children keep track of and estimate the position of nonvisible objects so that they can effectively move through their environment without getting lost. These skills are fundamental to managing everyday tasks, but little is known about how they are acquired by young children. Two studies use a task that requires young children to search for an object hidden in sandboxes that differ in size and shape. Children's performance in finding the hidden objects in the different sandbox tasks will reveal the generality and limitations of their knowledge about space during the first three years of life. The research will generate new knowledge about children's spatial behavior, while also seeking points of integration between two different theories of spatial behavior. There is a gap in our existing knowledge about spatial behavior in children between 1 to 3 years of age. This is a time in development that includes important advances in the growth of movement skills and thinking skills that should influence how children keep track of locations while they move through space and how this ability develops. The project is guided by two different theories, one that attempts to explain adult spatial behavior and another that attempts to explain children's spatial behavior. Specific predictions made by these two theories will be tested. The results of the studies may support an integrated account of early spatial development that can explain a wider range of spatial behaviors than either theory can now explain. This POWRE award will permit the investigator, an associate professor, to resume her research career after spending the last few years on sabbatical leave and assisting in university administration. These activities, while important in other respects, took a toll on her career advancement and professional growth. She will now get back on track to a productive research program, which will put her in an excellent position for academic advancement and leadership in her field.